1. Field of the Invention
This invention relates to hinges and has particular reference to improvements in hinges for spectacles frames.
2. Discussion of the Prior Art
Metal hinges used to pivotally connect temples to spectacles frame fronts of ophthalmic mountings are traditionally difficult and costly to manufacture and suffer the drawbacks of screws backing out with looseness of temple fit which is commonly referred to in the art as "drop temple". In the alternative of tightening against "drop temple", undue binding and/or roughness of pivoting action usually results from the metal-to-metal contact between leaves of the hinge barrel. Hinges of this type are illustrated in U.S. Pat. Nos. 825,483; 1,708,202; 1,844,143 and 3,826,565.
In addition to the high cost of equipment, repair and maintenance required to perform the operations necessary to produce and assemble spectacles hinges of the aforesaid types, the close tolerance control needed for assembly imposes the added drawback of uneconomical scrap yield. Tolerance accumulation from machining and electroplating build-up can render interleaving of the hinge components unusually difficult if not impossible in some cases.
In attempts to overcome the backing out of hinge screws and drop temples, various forms of non-metallic bushings or sleeves have been placed around the hinge screw which, when longitudinally compressed by tightening of the screw do relieve some of the screw loosening and drop temple problems. Non-metallic hinge pins have also been used. The drawbacks of metal-to metal contact between confronting surfaces of leaves of the hinge barrel are, however, not overcome and hinge binding or roughness of pivoting action can continue to be problematic. The structures depicted in U.S. Pat. Nos. 2,826,668; 2,926,381; 2,939,168; 3,042,961; 3,349,430 and 3,546,735 are exemplary of this latter type of hinge construction.
The insertion of washers between leaves of hinge barrels, non-metallic hinge leaf boots and screw lock washers can also relieve drop temple problems, improve the pivoting action of spectacles hinges and at least to some extent relieve machining tolerances. These schemes, however, do not overcome the need for expensive hinge making equipment, its costly repair and maintenance. Furthermore, the costs of manufacturing the added number of minute hinge parts, their inventorying, special handling and ungainliness in assembly renders this approach to spectacles hinge construction relatively impractical and certainly uneconomical. U.S. Pat. Nos. 2,428,645; 2,192,208 and 3,427,681 are respectively illustrative of the screw lock washer, the interleaving washer and hinge leaf boot scheme.
Another prior art approach to avoiding problems of metal-to-metal hinge leaf interfitting is illustrated in U.S. Pat. Nos. 3,104,416 wherein a complete hinge component, i.e. hinge plate and all ears, is formed of plastic and is intended to interfit with a similar but all metal second hinge component. The advantages of this plastic-to-metal hinge leaf interfitting are, however, largely outweighed by the lack of ruggedness and resistance to breakage of the all plastic hinge component. In particular, the thin sections of joinder of ears of the main plate in the all plastic component are susceptable to breakage during spectacle frame assembly or in subsequent use. The minuteness of hinge size required in spectacle construction and considerable abuse needed to be resisted as well as the need for angular adjustment under use redners all plastic hinges or hinge halves impractical for long term use and particularly relatively unsuitable for use in high quality prescription ophthalmic mountings. Therein the weight of greater thickness and bulk of corrective lenses and/or ruggedness of frame structure dictate a need for the more durable metal or metal reinforced hinge components having a capability of withstanding the sometimes excessive handling and wearing abuses. Inexpensive sunglass spectacles having relatively short service lives are commonly provided with molded cast and/or machined all plastic hinges. Those illustrated in U.S. Pat. Nos. 3,156,756; 3,524,216 and 3,744,887 are exemplary. All plastic hinges serve the immediate purpose of cheapness of construction required of variety store type structures which are not intended or expected to withstand the abuse of long service.
Other inexpensive hinge constructions intended mainly for the low cost sunglass frame or disposable safety spectacles are stamped from thin sheet metal and bent into final shape. The structures of expired U.S. Pat. Nos. 452,008; 452,009 and 2,745,314 are exemplary of types of structures still in use. These hinges, however, suffer the already discussed drawbacks of metal-to-metal interleaving.
With the foregoing in view, the present invention has a principal objective of providing spectacles hinges of exceptionally high quality and of dependable long service life but of an uniquely simple and inexpensive construction which will overcome the traditional problems of screw back-out, drop temple, barrel binding and/or roughness of pivoting action all without need for expensive manufacturing equipment, its attending high repair and maintenance costs and difficult or tedious assembly operations.
It is another object of the invention to overcome the heretofore need for separately and uneconomically performed milling, blanking, drilling, piercing and tapping operations in the manufacture of high quality long service life spectacles hinges.
Still another object is to overcome prior art problems of interfitting barrel leaves in hinge assembly procedures and to avoid metal-to-metal hinge leaf contact while affording the sureness of a metal supported hinge construction needed for long service life in high quality ophthalmic spectacles and further with applicability to any and all types of spectacles.
Other objects and advantages of the invention will become apparent from the following description.